Compilare: user.cpp: In function ‘void solve(int)’: user.cpp:130:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s.size(); ++i) ^ user.cpp:132:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(k<s.size() && val[s[i]] == val[s[k]]) ^ user.cpp:148:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s.size() && val[s[i]] <= val[node]; ++i) ^